92 Q heater temperature problem

[kdkrone]

Recently, I seem to be unable to raise my heated air temperature above about 76 or 77 degrees despite turning the temperature up to max (85 degrees) on the dash control LED.

Is this corrected with an adjustment or does it require a new controller? Everything else on the controller works just fine.

ThanksKen K

[911/Q45]

There are several sensors involved that are reasonably priced, fairly easy to replace and likely to be involved. The FSM has extensive info on this and many other things, get one soonest.

[STECH]

Sounds like it might be the intake temp. sensor in the evap. case.it might be shorted out.

[kdkrone]

Thanks for the recommendation to check the manual---silly me. I did not realize that there was a self-diagnotic program.

I ran the program and the only potential problem was a flashing 25, which refers to the sunlight sensor. As I was testing at sunset and had no 60W (or greater) light, I must assume that this was not the problem.

Anyway, everything else worked just fine so I shut off the system and re-started the car. The heat seems to be working just fine now, so not only may the system be diagnositic, it may be reparative, as well....!!

We shall see.

Thanks again for the suggestion,Ken K

[Q451990]

Remember that you can adjust the "trim" on it upward by +5F. The Q's heat seems lukewarm compared to other cars with manual climate control. I think a lot of it is the designer's insistance that heat comes from the floor vents instead of the dash vents unless you override the floor vents.

Heath

[kdkrone]

"Remember that you can adjust the "trim" on it upward by +5F. The Q's heat seems lukewarm compared to other cars with manual climate control. I think a lot of it is the designer's insistance that heat comes from the floor vents instead of the dash vents unless you override the floor vents."

Yes, I agree that it has always seemed lukewarm, as you say.

By adjusting the trim do you mean that I can raise the temperature 5 degrees? If so, how? (Is it in the "FSM"?)

ThanksKen

[Q45tech]

With the coolant temp at 176F, I have measured 130F air coming from the lower ducts depending on fan speed.......hardly luke warm. The heater core is a very decent size for interior volume and glass losses.

Many Q don't warm up enough [in winter] because the thermostat is old [older than 3-4 years] and constantly open some. Important to check coolant temp [Consult] when drive 60 mph [and 20F] outside.

Many old AC evaporator are partially clogged with dog/cat/rat/human hair -general funky stuff so the air flow is reduced [as it is in summer]. Old fan turn slower with age.............it isn't like new till everything is like new.

Real pain to use Consult [as it won't conduct many test until coolant is 176F]............."Sir we need to change your thermostat first before we can diagnose the rest".......just like the KS failure......."Sir you must spend $1,000-$1,400 [with plenum hoses] to replace the KS and harness before we can diagnose the other components".............first hard code locks out other tests till it is fixed.

Thus you see the need for my KS or coolant temp emulator, just to get Consult/ecu to ignore these fist two common major faults.

[kdkrone]

Q45tech,

Thanks for responding. I would have no problem popping for a new thermostat; I don't know that I have ever had it replaced in the past 12 years (90,000 original miles). As I reflet on what you have written, the heat blowing from the upper vents (when I use manual) when the car is idling is about 120+ degrees; it is on the highway that it is lower. I will take a thermometer with me on the way to work today to check it. Outside air here in California is about 40 degrees.

<<<Thus you see the need for my KS or coolant temp emulator, just to get Consult/ecu to ignore these fist two common major faults>>>

Two stupid questions: 1, what dose KS stand for? 2, do you make a piece of equipment that feeds some info into the system that emulates the coolant temperature?

Not so stupid question: how difficult is it to get at the AC evaporator to clean it? (I have no children, no dogs, no cats that are ever in the car, and I am bald.. but there might still be some hair there)

Q451990 wrote: <<<Remember that you can adjust the "trim" on it upward by +5F.>>>

How is the temperature adjusted if I choose to increase it?

ThanksKen K

[Jesda]

http://www.q45.org/cleanevap.html

[kdkrone]

Excellent! Thank you for the URL. I did not know about the Q45.org site.

KK

[Q451990]

The trim adjustment is in the service manual in the same section as the diagnostics. I don't have it in front of me at the moment.

KS Stands for "Knock Sensor"

Heath

[kdkrone]

I may not need to fiddle with the trim adjustment. Since doing the diagnostic test, my Q seems to have increased the air temp. On the way to work this AM, with an ambient temp of 45 and the engine warmed up, she was putting out air through the upper dash outlets at a temp of 133 degrees. That having been said, I will use the instructions on how to clean the evaporator coils.

ThanksKen K

[Q45tech]

The KS [knock sensors] and ecu coolant temp sensor share the same under plenum wiring harness..........and off engine assembly connector.

The coolant temp sensor is just an extremely accurate thermatic variable resistor, while the KS are piezo microphones that are shielded [microphone wire] but use the mounting bolt and head surface as the ground [return] connection. They must be bolted in place to work, mounting torque is critical as while the ground may be in place the sandwich torque affects sensitivity.